Using SABRE Hyperpolarized ¹³C NMR Spectroscopy to Interrogate Organic Transformations of Pyruvate

Signal amplification by reversible exchange (SABRE) is a hyperpolarization technique that uses a metal complex to catalytically transfer magnetization from parahydrogen to molecules of interest. SABRE is used here to monitor the decarboxylation of sodium pyruvate-1,2-[¹³C₂] at a 15 mM concentration to form ethanoic acid and CO₂ upon reaction with hydrogen peroxide (150 mM). The rate constant of this reaction is determined by hyperpolarized ¹³C SABRE-NMR spectroscopy as 0.056 ± 0.003 dm³ mol^-1 s^-1 at 298 K and is comparable to that determined from thermal ¹H NMR (k = 0.050 ± 0.003 dm³ mol^-1 s^-1) and UV measurements (k = 0.053 ± 0.001 dm³ mol^-1 s^-1). The hyperpolarized reaction intermediate 2-hydroperoxy-2-hydroxypropanoate is detected in a single scan hyperpolarized ¹³C NMR spectrum. This work highlights how SABRE hyperpolarization can be used as a tool for the precise monitoring of chemical transformations by hyperpolarized NMR spectroscopy.